...

src/aarch64-linux-flush-dcache/mod_entry.c

@@ -6,7 +6,6 @@
 #include "linux/gfp_types.h"
 #include "linux/rcupdate.h"
 #include <asm-generic/cacheflush.h>
-#include <asm/cacheflush.h>
 #include <linux/irqflags.h>
 #include <linux/mm_types.h>
 #include <linux/mmap_lock.h>
@@ -23,6 +22,7 @@ module_param_named(pid, param_pid, int, 0644);
 static unsigned long param_vmaddr;
 module_param_named(addr, param_vmaddr, ulong, 0644);
 
+static void **page_addrs;
 static void *page_addr = NULL;
 
 /* Design:
@@ -121,7 +121,7 @@ int _flush_dcache_init_devfs(void)
 
 }
 
-int _flush_dcache_init_backend(void)
+int _flush_dcache_alloc_pages(int page_nr)
 {
 	page_addr = alloc_page(GFP_USER);
 	if (!page_addr)
@@ -133,13 +133,13 @@ ret_err_alloc_failed:
 	return -ENOMEM;
 }
 
-static int flush_dcache_open(struct inode *inode, struct file *filp)
+static int flush_dcache_fops_open(struct inode *inode, struct file *filp)
 {
 	filp->f_mode |= FMODE_CAN_ODIRECT;
 	return generic_file_open(inode, filp);
 }
 
-static int flush_dcache_mmap(struct file *filp, struct vm_area_struct *vma)
+static int flush_dcache_fops_mmap(struct file *filp, struct vm_area_struct *vma)
 {
 	/* Check if vma has mm backing -- e.g., non-kthread */
 	if (!vma->vm_mm)
@@ -171,8 +171,8 @@ ret_err_wrong_size:
 
 const struct file_operations flush_dcache_fops = {
 	.owner = THIS_MODULE,
-	.open = flush_dcache_open,
-	.mmap = flush_dcache_mmap
+	.open = flush_dcache_fops_open,
+	.mmap = flush_dcache_fops_mmap
 };
 
 // const struct vm_operations_struct flush_dcache_vmops = {

src/aarch64-linux-flush-dcache/mod_entry_1.c

@@ -0,0 +1,163 @@
+#include <linux/rcupdate.h>
+#include <linux/vmalloc.h>
+#include <linux/list.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/mm_types.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+
+struct my_shmem_page {
+	struct page *page;
+	struct list_head list;
+};
+static DEFINE_MUTEX(my_shmem_pages_mtx);
+
+/* [!] READ/WRITE UNDER LOCK */
+static LIST_HEAD(my_shmem_pages);
+
+/* [!] READ/WRITE UNDER LOCK */
+static size_t my_shmem_page_count = 0;
+
+/* Virtual Memory Area Operations...
+ * ============================================================================
+ */
+static vm_fault_t my_shmem_vmops_fault(struct vm_fault *vmf)
+{
+	pgoff_t page_offset = vmf->pgoff;
+	phys_addr_t _phys;
+	size_t old_shmem_page_count;
+
+	mutex_lock(&my_shmem_pages_mtx);
+	old_shmem_page_count = READ_ONCE(my_shmem_page_count);
+	if (unlikely(page_offset > old_shmem_page_count)) {
+		/* IMPOSSIBLE -- programming error or wrong assumption... */
+		mutex_unlock(&my_shmem_pages_mtx);
+		goto err_ret_impossible_count;
+	}
+
+	if (page_offset < old_shmem_page_count) {
+		/* Offset in range, return existing page */
+		pr_info("[%s] Found remappable page offset %lu.",
+			__func__, page_offset);
+
+		// We won't delete elements from list here!
+		struct my_shmem_page *page_entry;
+		list_for_each_entry(page_entry, &my_shmem_pages, list) {
+			if (!page_offset)
+				break;
+			page_offset--;
+		}
+		// Found correct page entry, remap
+		get_page(page_entry->page);
+		vmf->page = page_entry->page;
+		_phys = page_to_phys(page_entry->page);
+
+		mutex_unlock(&my_shmem_pages_mtx);
+		goto ok_ret_remapped;
+	}
+
+	/* Otherwise, allocate the new page */
+	for (int i = 0; i < page_offset - old_shmem_page_count; i++)
+	{
+		/* The loop is misleading -- this loops exactly once! */
+		// Allocate page handle in kernel
+		struct my_shmem_page *new_page = kzalloc(
+			sizeof(struct my_shmem_page), GFP_KERNEL);
+		if (!new_page) {
+			mutex_unlock(&my_shmem_pages_mtx);
+			goto err_ret_no_kmem;
+		}
+
+		// Allocate page in virtual memory
+		void *addr = vmalloc_user(PAGE_SIZE);
+		if (!addr) {
+			mutex_unlock(&my_shmem_pages_mtx);
+			goto err_ret_no_vmem;
+		}
+		new_page->page = vmalloc_to_page(addr);
+
+		// List maintenance: add and incr. size
+		list_add(&new_page->list, &my_shmem_pages);
+		my_shmem_page_count++;
+
+		// Fill in allocated page entry
+		get_page(new_page->page);
+		vmf->page = new_page->page;
+		_phys = page_to_phys(new_page->page);
+	}
+	mutex_unlock(&my_shmem_pages_mtx);
+	goto ok_ret_allocated;
+
+err_ret_impossible_count:
+	pr_crit("[%s] IMPOSSIBLE list count %ld > %ld "
+		"-- no way one fault services multiple page!!!",
+		__func__, page_offset, old_shmem_page_count);
+	return VM_FAULT_ERROR;
+err_ret_no_kmem:
+	pr_err("[%s] Cannot allocate `struct my_shmem_page` in kernel memory.",
+		__func__);
+	return VM_FAULT_OOM;
+err_ret_no_vmem:
+	pr_err("[%s] Cannot allocate requested page for virtual memory.",
+		__func__);
+	return VM_FAULT_OOM;
+ok_ret_remapped:
+	if (vmf->vma->vm_mm) {
+		rcu_read_lock();
+		struct task_struct *fault_owner = vmf->vma->vm_mm->owner;
+		pr_info("[%s] Remapped phys: 0x%llx -> virt@PID(%d): 0x%lx.",
+			__func__, _phys, fault_owner->pid, vmf->address);
+		rcu_read_unlock();
+	}
+	return 0;
+ok_ret_allocated:
+	if (vmf->vma->vm_mm){
+		rcu_read_lock();
+		struct task_struct *fault_owner = vmf->vma->vm_mm->owner;
+		pr_info("[%s] Allocated phys: 0x%llx -> virt@PID(%d): 0x%lx.",
+			__func__, _phys, fault_owner->pid, vmf->address);
+		rcu_read_unlock();
+	}
+	return 0;
+}
+
+static const struct vm_operations_struct my_shmem_vmops = {
+	.fault = my_shmem_vmops_fault,
+};
+
+/* File Operations...
+ * ============================================================================
+ */
+// static int my_shmem_fops_open(struct inode *inode, struct file *filp);
+
+static int my_shmem_fops_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	vma->vm_ops = &my_shmem_vmops;
+	return 0;
+}
+
+static const struct file_operations my_shmem_fops = {
+	.owner = THIS_MODULE,
+	.mmap = my_shmem_fops_mmap,
+	.fsync = noop_fsync,
+};
+
+/* Module init & exit...
+ * ============================================================================
+ */
+static int __init my_shmem_init(void)
+{
+	int reg_cdev_ret = register_chrdev(0, "my_shmem", &my_shmem_fops);
+	if (reg_cdev_ret != 0)
+		goto err_ret_cdev_reg_failed;
+	return 0;
+
+err_ret_cdev_reg_failed:
+	pr_err("[%s] Cannot register character dev -- error code %d.",
+		__func__, reg_cdev_ret);
+	return reg_cdev_ret;
+}